Influence of Surface Defect Structure on the Underpotential Deposition of PbMonolayers at Ag(111)

摘要

The underpotential deposition (upd) of Pb monolayers at Ag(111) thin-filmelectrodes in perchlorate solutions has been investigated as a function the substrate defect structure. Ag(111) films were grown expitaxially on muscovite mica by thermal evaporation and annealed at 300 deg C at 10(exp -6) torr for periods between 0 and 12 hours. Glancing angle X-ray diffraction and scanning tunneling microscopy indicate that thermal annealing significantly increases the degree of film crystallinity and smoothness. A more ideal voltammetric response for the upd of Pb was obtained using Ag thin-film electrodes that were annealed for periods longer than 6 hr. Specifically, the width of the upd voltammetric wave, as well as the splitting between the cathodic and anodic peaks, were found to decrease with an increase in film annealing time. Surface roughness factors (defined as the ratio of the electrochemically-active area relative to the geometric area) for the Ag(111) films decreased from 1.15 for unannealed films to